New study finds ideal weight loss target for obese patients before knee surgery

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weight loss before knee replacement surgery

If you’ve been classed as morbidly obese (which according to the NHS is a BMI of over 40) and you’re awaiting knee replacement surgery, you’ve already been told that losing weight is a must. Makes perfect sense: after surgery, your knee will be temporarily weaker until it completely mends, and the more weight you can keep off it, the better.

The question is; how much weight should you be aiming to lose to maximise your chances of a short recovery period? Many medical experts advise patients to lose between five and ten pounds before going under the knife, but a new study claims that for the full benefit, you should be aiming at dropping 20 pounds beforehand.

The study, conducted by a research team from the Geisel School of Medicine at Dartmouth College in New Hampshire, involved data harvested from 203 patients who were either 100 pounds over their ideal body weight, had a BMI of over 40, or had a BMI of 35 and also suffered from high blood pressure or diabetes prior to their total knee arthroplasty procedure.

Well worth the (loss of) weight

The team tracked the study group’s weight loss regime in the three-month run-up to their surgery and discovered that in the three months leading up to their TKA procedure, 41% of the patients lost at least five pounds, 29% lost at least 10 pounds and 14% lost at least 20 pounds. After the surgery, 27 patients were no longer morbidly obese, although 23 of those were still severely obese (with a BMI between 35 and 40).

The research team presented their findings t the annual meeting of the American Academy of Orthopaedic Surgeons last month, and reported that – when compared to patients who did not lose 20 pounds – the patients who did had a 72% possibility of being discharged to a rehab facility and 76% lower odds of staying in the hospital for at least four days.

Ten pounds isn’t enough

While there were no differences in operative time or physical function improvement for the two groups, the researchers noted that losing five or ten pounds did not make a difference for any outcome.

“Twenty pounds is the magic number, based on our evidence,” claimed study leader Dr Benjamin Keeney. “This is even after accounting for age, gender, and other diagnoses besides obesity, as well as baseline physical and mental function.” He pointed out that the people who lost twenty pounds and reaped the benefit of an improved outcome were still very obese at the time of surgery – and that most of them even gained a lot of that weight back afterwards – but even so, the temporary loss of weight still led to a better outcome.

“What this study is telling us is that morbidly obese patients who lose at least twenty pounds before knee replacement are going to come home from the hospital faster and are much less likely to go on to be discharged to a facility,” he claimed. “This is a concrete goal, instead of telling patients we won’t operate unless they get a BMI of 40 – which for some patients can be a loss of 50 to 100 pounds.”

For more advice on how best to prepare for knee replacement surgery, call 0203 195 2443 to arrange a consultation at Mr Jonthan Webb’s London orthopaedic clinic.